1. Field of the Invention
The present invention relates to internal combustion engines, in particular diesel engines but also gasoline or petrol engines and particularly a method and apparatus for reducing the fuel consumption of the engine.
2. Description of Related Art
Internal combustion engines such as diesel engines and gasoline, also known as petrol, engines are widely used to power vehicles including trucks and cars. Intake air and fuel constitute a combustion charge which is burned in the engine to produce mechanical energy which imparts rotational movement to the crankshaft to propel the vehicle and power other systems of the vehicle.
Intake air is supplied to the internal combustion engine by way of an intake air system which includes sections of an intake air conduit or passage and various components depending on the type of engine. In the case of a diesel engine, the intake air system typically includes an airbox which is normally located in the engine compartment and into which enters ambient air from outside the vehicle. The intake air conduit or passage carries the intake air from the airbox ultimately to an intake air manifold which is in communication with the air intake ports of the combustion chambers of the engine.
A first section of the intake air conduit or passage is typically connected to a compressor of a turbocompressor to increase the pressure and therefore density of the intake air which is supplied by one or more other sections of the intake air conduit or passage to the intake air manifold. In a diesel engine the intake air is drawn from the manifold directly into the combustion chamber or chambers of the engine during the expansion stroke and compressed and mixed with the fuel during the compression stroke. After combustion of the fuel air mixture, the products of combustion or exhaust gases, exit the combustion chamber or chambers to an exhaust manifold and then to an exhaust gas pipe typically equipped with a muffler and catalytic converter. In addition, an intercooler for cooling the intake air is often provided between the compressor and the intake air manifold.
For a gasoline or petrol engine, different components are disposed along the intake air conduit or passage. Intake air and fuel are mixed in a carburetor before entering the combustion chamber(s) or directly injected into the chamber(s). The turbocharger is optional equipment and may be replaced by a supercharger and intercoolers are normally not used.
The internal combustion engine for a car or truck is generally located at the front of the vehicle inside an engine compartment which is covered by a metal access hood. A running combustion engine which has an engine block made of cast iron or aluminum gives off a large amount of heat which is conducted or radiated throughout the engine compartment. Temperatures in the engine compartment may exceed 300.degree. F. The heat generated inside the engine compartment is conducted and/or radiated intake air conduit or passage which in turn considerably increases the temperature of intake air delivered to the engine which may exceed 200.degree. F.
When the engine is equipped with a turbocharger the high temperature and velocity exhaust gases (temperature is 200.degree. F.) from the engine block are fed to a turbine which drives the compressor used to increase the density of the intake air. The turbine of a turbocharger operates at very high temperatures (in the excess of 800.degree. F.) and the turbocharger generates additional intense radiant heat inside the engine compartment. Also, the deviation of the exhaust gas conduit to carry those gases to and from the turbine increases the heat transfer surface between the exhaust gas conduit and the time the exhaust gases remain inside the engine compartment.
Insulating wraps have been used for exhaust headers to decrease the heat generated inside the engine compartment, such as those manufactured by Design Engineering, Inc. and Thermo-Tec. Such conventional high temperature fiber insulating wraps are wrapped around the tubes of the header and secured with clamps. They increase the temperature of the exhaust gases and improve engine performance. By increasing the temperature of the exhaust gases, they also tend to reduce the heat radiated to the engine compartment.
The cost of operating vehicles is high owing the high cost of fuel for internal combustion engines. Internal combustion engines also have poor fuel efficiency. The cost of fuel for powering internal combustion engines of cars and trucks is a major concern for the industrialized world. The problem of fuel efficiency of internal combustion engines is long standing.
An object of the present invention is to improve significantly fuel efficiency of diesel or gasoline internal combustion engines for cars and trucks, as well as ships, boats or other means of locomotion, and for other commercial and industrial use, such as for power generators and industrial pumps.
Another object of the invention is a method and system of improving fuel efficiency of internal combustion engines at relatively low cost, and which may be retrofitted or adopted as part of original equipment.
Another object of the present invention is a method and system for improving fuel efficiency of internal combustion engines regardless of type or construction of the engine, the construction or makeup of the intake air system and in particular the intake air conduit or passage and components disposed along the intake air conduit or passage, including equipment such as a turbocharger, supercharger or intercooler.
According to an aspect of the present invention, a method and system are provided for reducing or minimizing the increase the temperature of intake air flowing through the intake air system by wrapping or covering the intake air conduit or passage to the combustion chamber(s) of the engine with thermal shielding to protect it from the heat radiated and conducted inside the engine compartment.
According to another aspect of the invention, thermal shielding is selectively wrapped on the turbine and compressor of the turbocharger to prevent turbine heat being radiated and conducted to the engine compartment and in the case of the compressor to shield the intake air being compressed from the intense turbine heat and elevated heat inside the engine compartment.
According to still another aspect of the invention, the exhaust manifold is also wrapped or covered with thermal shielding reducing the heat radiated and conducted by the exhaust gases to the engine compartment and thereby to the intake air conveyed by the intake air system until it reaches the combustion chamber(s) of the engine.
The intake air conduit or passage is wrapped with a thermal shield comprising an outer heat radiating or reflecting layer and an inner thermal insulating layer. The radiating or reflecting layer radiates heat away from the intake air conduit or passage and thereby away from the intake air flowing therethrough. The thermal insulating layer provides a thermal gradient between the higher temperature outer thermal radiant layer and the conduit or passage around which the thermal shield is wrapped whereby the temperature of the inner surface of the thermal insulating layer has a substantially lower temperature than the temperature of the outer radiant layer. For example, temperatures of the order of 500.degree. F. may be found on the outer radiant layer and intake air temperatures of the order of 100.degree. F. may be found on the inner surface of the insulating layer.
For a diesel engine, the intake airbox may be wrapped with thermal shielding separately from the intake air conduit or passage sections and may comprise a plurality of mating or overlapping pieces of thermal shield corresponding to the size and configuration of various portions of the intake airbox. The inner face of the pieces of thermal shield preferably has an adhesive coating for facilitating the attachment to the corresponding part of the intake airbox. Similarly, the thermal shield for the intake air conduit or passage also has an adhesive coated inner face for facilitating the attachment to the outside surface of the intake air conduit or passage. Such a thermal shield is both lightweight and flexible permitting it to be adapted to the contour of surfaces to be wrapped. In addition, a metallic, and in particular an aluminum foil, adhesive tape may be applied over the thermal shield to cover the seams between pieces or even over some or the rest of the otherwise exposed thermal shield.
Similarly, the heat radiating components in the engine compartment, specifically the exhaust manifold, turbine and compressor of the turbocharger are wrapped or covered with multilayered insulating and radiating heat shields. Such thermal shields comprise an outer heat reflecting or radiating aluminized fabric and one or preferably two layers of thermal insulating material, in particular a non-woven web of insulating material and a woven cloth of insulating material, and an inner layer of wire mesh for reducing wear of the overlying layer of (friable), thermal insulating material which is subject to vibrations from the engine or other parts of the vehicle. Such a thermal shield will be thicker than the thermal shield used for shielding the intake air conduit or passage but sufficiently bendable to conform generally to the configuration of the exhaust manifold, turbine and compressor, respectively. Such a thermal shield may be secured with wires, safety straps or clamps of suitable heat resistant material, in practice of metal. The turbine and the compressor will preferably not be entirely wrapped with thermal shielding in order to leave exposed the bearings to avoid overheating and seizure. To avoid overheating, the side of the compressor housing remote from the turbine is preferably not wrapped with this heat shield.
The underside of the hood of the vehicle is also preferably insulated with the same thermal shield material used for the intake air conduit or passage and is likewise provided with an adhesive coated inner face which so it may be applied directly to the inside surface of the hood. The shielding of the hood will protect the engine compartment from the sun, particularly useful in hot climates. The shielding of the hood will also prevent heat from radiating through the hood, so that it is channeled downwardly out of the engine compartment to ambient air flowing beneath the vehicle.
Finally, the fuel lines may be insulated to protect them from the high temperatures in the engine compartment thereby preventing fuel vapor lock.
Testing on diesel engines wrapped with thermal shields in accordance with the invention resulted in a reduction of 15-20% in fuel consumption.